For example, CAFs rely on the activation of HIF-1 to secrete carbonic anhydrase (CAIX), which raises the acidity of extracellular matrix; CAFs secrete MMP-2/9 [14], therefore inducing the epithelial-mesenchymal transition (EMT) in tumour cells and enhancing the migration ability of tumour cells [15]. This evidence concerns the gene MMP2 and neoplasm.